graymatter

Gray matter, sometimes written as graymatter, is a pinkish-gray region of the central nervous system rich in neuronal cell bodies, dendrites, unmyelinated axons, glial cells, and capillaries. The term contrasts with white matter, which contains myelinated axons. In the brain, gray matter forms the cerebral cortex on the surface and several deep structures such as the basal ganglia, thalamus, and hypothalamus. In the spinal cord, gray matter sits centrally in an H-shaped region, containing dorsal horns (sensory) and ventral horns (motor) as well as interneurons.

Functionally, gray matter is where information processing occurs: synaptic integration, neuronal computation, and the initiation of motor commands. The cerebral cortex supports perception, thought, memory, and voluntary movement, while deep gray matter participates in movement control and sensorimotor integration.

Gray matter develops from neural progenitor cells during embryonic and early postnatal life and can change in thickness and density with age, experience, and disease. In imaging studies, gray matter volume and cortical thickness are common metrics; differences in gray matter are linked to aging, learning, and various neurological and psychiatric conditions.

Clinical relevance: many neurodegenerative and neuropsychiatric disorders show changes in gray matter, including cortical thinning in Alzheimer’s disease and reductions in hippocampal and cortical gray matter. Disorders such as multiple sclerosis affect white matter preferentially but can indirectly impact gray matter.